The proton-proton weak capture in chiral effective field theory

TL;DR

This paper calculates the proton-proton weak capture S-factor using chiral effective field theory, incorporating electromagnetic corrections and fixing low-energy constants to match experimental data, providing precise theoretical predictions.

Contribution

It presents a detailed chiral EFT calculation of the proton-proton weak capture S-factor including electromagnetic effects and P-wave contributions, with quantified uncertainties.

Findings

S(0) = (4.030 ± 0.006) x 10^{-23} MeV fm^2

P-wave contribution is 0.020 x 10^{-23} MeV fm^2

Theoretical uncertainty stems from LEC fitting and cutoff dependence.

Abstract

The astrophysical S-factor for proton-proton weak capture is calculated in chiral effective field theory over the center-of-mass relative-energy range 0--100 keV. The chiral two-nucleon potential derived up to next-to-next-to-next-to leading order is augmented by the full electromagnetic interaction including, beyond Coulomb, two-photon and vacuum-polarization corrections. The low-energy constants (LEC's) entering the weak current operators are fixed so as to reproduce the A=3 binding energies and magnetic moments, and the Gamow-Teller matrix element in tritium beta decay. Contributions from S and P partial waves in the incoming two-proton channel are retained. The S-factor at zero energy is found to be S(0)=(4.030 +/- 0.006) x 10^{-23} MeV fm^2, with a P-wave contribution of 0.020 x 10^{-23} MeV fm^2. The theoretical uncertainty is due to the fitting procedure of the LEC's and to the cutoff dependence.